The present invention relates to a method for manufacturing a resin thin film, in particular, a method for forming a resin thin film on a supporting base by evaporating a resin material so that the resin material is deposited on a surface of the supporting base.
Thin films play an important part in a wide range of aspects of current society and are utilized in a variety of areas in our daily life such as wrapping papers, magnetic tapes, capacitors, semiconductors or the like. The basic trends of technology including high performance and miniaturization in recent years cannot be discussed without referring to such thin films. At the same time, various methods for forming a thin film have been under development to satisfy industrial demands. For example, continuous winding vacuum evaporation, which is advantageous to high-speed mass production, has been performed to form the thin films for use in wrapping papers, magnetic tapes, capacitors or the like. In this case, a thin film having desired characteristics can be formed by selecting an evaporation material and a substrate material to meet the purpose of the thin film to be formed and introducing a reactive gas in a vacuum chamber, if necessary, or forming the thin film while applying an electric potential to the substrate.
A method for forming a resin thin film by coating a supporting base with a resin material that is diluted with a solvent is known as a method for obtaining a resin thin film. Reverse coating or die coating is used industrially, and generally the material is dried and cured after coating. The thickness of coating by a common coating technique is several xcexcm or more immediately after coating. Therefore, the material is required to be diluted with a solvent to form a very thin resin film. Nevertheless, the lower limit of the thickness of the resin thin film formed by these methods is often around 1 xcexcm, although it may be varied depending on the material used. It is often difficult to obtain a thickness less than 1 xcexcm. Furthermore, the solvent dilution is not preferable, because the dilution with a solvent causes defects readily in a coating film after drying due to the evaporation of the solvent, as well as in view of environmental protection. Therefore, a method for forming a resin thin film without the solvent dilution and a method by which a very thin resin film can be obtained stably are in demand.
As a method to solve this problem, a method for forming a resin thin film in a vacuum has been proposed. For example, EP 0 808 667 discloses the following method. A resin material is supplied to a heating member so as to be heated and evaporated in a vacuum. Then, the resin material is deposited on a moving supporting base so that a resin thin film is formed on the supporting base continuously. This method permits the resin thin film to be formed without void defects and the solvent dilution to be eliminated.
However, in the method disclosed in EP 0 808 667, the amount of the resin material evaporated is not stable, so that the obtained resin thin film cannot have a uniform thickness. In addition, the properties of the obtained resin thin film are not stable, or a resin thin film having desired properties cannot be obtained. In particular, the demand for the characteristics of the resin thin film that is to be used in electronic components have become increasingly high. The problems as described above reduce the yield of the products and increase the cost.
The inventors of the present invention studied to solve the problems in the conventional method for manufacturing a thin film. As a result, they found out that these problems were caused by the manner in which the resin material is supplied to a heating member.
More specifically, conventionally, the resin material is supplied to a heating member after the resin material is atomized with an ultrasonic transducer, a spray nozzle, or a mechanical atomizer.
However, in atomization with an ultrasonic transducer, it is difficult to atomize the resin material stably for a long time. Moreover, the resin material is heated by a mechanical external force applied to the resin material during the process of atomization, so that the nature of the resin material may be changed or the resin material may be solidified before being atomized. When the nature of the resin material has been changed, not only is the amount of the resin material evaporated not stabilized, but also a resin thin film having desired properties cannot be obtained. Furthermore, expensive equipment is required so that a cost-efficient resin thin film cannot be obtained.
Atomization with a spray nozzle is not suitable for a resin material having a large viscosity, so that the range of usable resin materials is limited. Moreover, since the particle size of the atomized resin material is relatively large, it is difficult to atomize the resin material stably when the amount of the resin material supplied is small, Therefore, it is difficult to form a resin thin film having a small thickness stably.
Furthermore, in atomization with a mechanical atomizer, an external force applied to the resin material for atomization is large, and therefore the resin material is heated. As a result, the nature of the resin material is changed or the resin material is solidified before being atomized. Furthermore, as in the case of the spray nozzle, since the particle size of the obtained resin material is relatively large, it is difficult to form a resin thin film having a small thickness stably.
It is an object of the present invention to provide a method for manufacturing a resin thin film that can solve the above problems and manufacture a resin thin film having a uniform thickness stably with simple apparatus at a low cost, by using a new method for supplying a resin material that can be substituted for the conventional supply method.
The present invention can have the following embodiments to achieve the above object.
A method for manufacturing a resin thin film according to a first embodiment of the present invention is a method for manufacturing a resin thin film by depositing an evaporated resin material on a surface of a supporting base. The method includes supplying a liquid resin material and a gas to a two-fluid nozzle by pressure; ejecting the resin material in the form of atomized particles toward a heating member by the two-fluid nozzle, thereby adhering the resin material to the heating member; and evaporating the resin material on the heating member to obtain the evaporated resin material.
A method for manufacturing a resin thin film according to a second embodiment of the present invention is a method for manufacturing a resin thin film by depositing an evaporated resin material on a surface of a supporting base. The method includes mixing a liquid resin material with a gas; ejecting the resin material in the form of atomized particles toward a heating member that is provided under a reduced pressure, thereby adhering the resin material to the heating member; and evaporating the resin material on the heating member to obtain the evaporated resin material.
According to the first and second embodiments of the present invention, the liquid resin material is ejected to a heating member by a two fluid nozzle or is ejected to a heating member that is provided under a reduced pressure after being mixed with a gas, so that the resin material in the form of atomized particles adheres to the heating member. Therefore, a mechanical external force that can affect the resin material in the process of atomization can be small, and therefore heat generation can be suppressed. As a result, the nature of the resin material can be prevented from changing, so that a resin thin film having desired properties can be obtained. Moreover, since the heat generation is small, the resin material is not solidified before being atomized. As a result, a resin thin film having a uniform thickness can be obtained stably. In addition, since the size of the obtained atomized particles is small, the amount of the resin material adhered to the heating member can be stabilized. As a result, the present invention can be used to manufacture a resin thin film having a very small thickness. In addition, since the range of usable resin materials is wide, a wide range of resin thin films having required properties can be manufactured by changing the resin material as appropriate. In addition, since the equipment for atomization is simple, a resin thin film can be manufactured at low cost.